FR2570912A1 - PHOTOELECTRIC RECEIVER WITH LOCAL ADAPTATION OF BRIGHTNESS - Google Patents

Abstract

PHOTOELECTRIC RECEIVER FOR A PICTURE DEVICE, IN PARTICULAR FOR A THERMAL IMAGING DEVICE, WITH LOCAL LUMINOSITY ADAPTATION. THE PHOTOELECTRIC RECEIVER INCLUDES AT LEAST ONE FIRST DETECTOR ELEMENT 1 FOR PUNCTUAL SCANNING OF THE IMAGE PRODUCED BY A RECEPTION OPTICAL AND AT LEAST ONE SECOND DETECTOR 2 ELEMENT ASSOCIATED WITH ONE OR MORE FIRST DETECTOR ELEMENTS, AND PRESENT A LARGE AREA OF SURFACE TO RADIATION TO SENSATE AT LEAST PART OF THE ENVIRONMENT OF AN IMAGE POINT SENSED BY A FIRST SENSOR ELEMENT.

Description

70912

  PHOTOELECTRIC RECEIVER WITH LOCAL ADAPTATION OF

THE LUMINOSITY

  The invention relates to a photoelectric receiver

  for a camera, in particular for a thermal imaging apparatus, with local adaptation of the brightness, as well as a method for this

  local adaptation of the brightness.

  By the "Frankfurter Allgemeinen Zeitung" of 18.06.75, N 137, on page 1 of the section "Natur und Wissenschaft", a device and a method for adaptation are known.

  local brightness for TV recordings.

  For this purpose, the shooting is done with two cameras

  who sweep the image in synchronism. One of the two

  meras is set fuzzy so that its signal corresponds to

  the average brightness of a small disk in the

  the vantage point of the image point itself. In an app

  such a special, not described in detail here, the signals of the two cameras are compared electronically so that the brightness scale is adapted point by point to the lighting conditions each time existing. The contrast between two neighboring image elements thus remains unchanged, but the dark parts

  of a scene can be, for example, de-

  stained parts lit and made more visible.

  In total, we obtain a dynamic increase

when shooting.

  As this method requires two full cameras (here: TV camera), it is therefore expensive. Even more expensive would be the process for

  thermal imaging devices including the detectors required

  their own cooling devices.

  The object of the invention is therefore to develop a photoelectric receiver for a camera, in particular a thermal imaging apparatus with local adaptation of brightness, which

  can work with a number of devices considered

  reduced. This result is achieved according to the invention

  the fact that the photoelectric receiver

  carries at least one first detector element for the

  punctual drawing of the image produced by an optics of

  reception and at least one second detector element

  assigned to one or more first detector elements and

  having a relatively large area sensitive to

  to capture at least part of the environment.

  an image point picked up by a first detector element. The method according to the invention is based on the fact that the second detector element determines an amplification factor with which the signals of the first detector element or elements are amplified for the first time.

formation of video signals.

  The photoelectric receiver and the method for the local adaptation of brightness n '. require that reception optics and, in the case of a thermal imaging apparatus, also only one cooling device, since the first and second detector elements may be placed in the same cooling tank. Moreover, so-called "neighborhood" operations to be performed for image enhancement and generally requiring a large number of electronic calculations, become easier to use.

  to achieve by optical means, in that the se-

  cond element detector is provided with a mask or a dia-

  opaque or semitransparent

  allows to locally modify the sensitivity to

  the surface of the detectors.

  The invention will be better understood using the

  description of embodiments taken as examples,

  but not limiting, and illustrated by the accompanying drawing, in which: Figure 1 shows a photoelectric receiver with a mounting for local adaptation of brightness;

  FIG. 2 represents a line of first ele-

  detector elements with second detector element arranged symmetrically with respect to the center;

  FIG. 3 represents a line of first ele-

  detector elements with second detector element arranged in front of the scanning direction; FIG. 4 represents an arrangement of first detector elements with a second detector element with a large

  surface arranged in front of the scanning direction.

  In the exemplary embodiment illustrated in FIG. 1, in the image plane of an unrepresented optical input and comprising a scanning device known per se and also not shown, there is one next to the another a first detector element 1 and a second detector element 2 placed in front of the scanning direction, these detectors being sensitive in the same spectral zone of interest and being hereinafter referred to as "detector" by abbreviation. infrared radiation, the two detectors made appropriately can be placed next to each other in the same cooling tank.The first detector 1 is used for point-by-point scanning of the image and is as small as possible for produce images

  high resolution. The second detector 2 must pre-

  to fully capture the environment of the point

  image captured by the detector 1. The signals of the

  2 are amplified in a preamplifier 3 and may optionally be used with timing - to control the amplification factor of an image amplifier 4

  which amplifies the signals of the detector element 1.

  output of the image amplifier 4 then appear the video signals that can be used for viewing

  or possibly for further processing. The com

  the amplification factor is in the sense of a local adaptation of the brightness, so that, for example in the case of a clear environment of an image point,

  therefore a signal of the detector 2, the am-

  amplification of the signal of the detector 1 is decreased and vice versa. The characteristic with which the amplification factor is modified depends on the preamplifier and the image amplifier, and may for example be linear in nature, exponential or of any other suitable nature. By methods of image enhancement by means of so-called "neighborhood" operations, it is known, for example, to evaluate the environment close to an image point.

  differently from more remote areas. This can be

  perform very simply by applying on the surface of the detector 2 a mask 2.1 which has transparencies

  locally different for the radiation to be received.

  In the exemplary embodiment shown, we want

  the corners of the square detector have another trans-

  than the central area. Other arrangements, for example concentric, can be obtained in the same way. Instead of the fixed configuration mask

  differences in local transparency, it is also possible to

  put in front of the detector 2 a liquid crystal diaphragm, for example made in the form of a matrix, whose elements can be electrically switched on

transmission or absorption.

  Figure 2 represents a line of first ele-

  detector elements 1 for scanning the image, a second detector element 2 for controlling the brightness of the entire line being arranged symmetrically with respect to the center thereof. This arrangement can for example be obtained by installing behind the reception optics or the scanning device, a ray divider in the output ray paths of which one

  place the line of

  and the second detector 2 with a large surface area

  triply relative to the optical axis each time considered. Another arrangement of a detector line consisting of first detector elements 1 and a second detector element 2 arranged in front of the scanning direction of a not shown scanning device is illustrated in FIG. command from the detector element 2 for the control of the brightness of the detector line would then arrive

  offset in time from the video signals cor-

  responders of the detector line. In the event of a high sweep rate and a short distance between the first and second detector elements, this may not be important; by means of organs

  time for the control signals, we can always

  here too realizing a correction in real time

for controlling the brightness.

  Another arrangement of first and second detector elements is illustrated in FIG. 4. Here, the first detector elements 1 form an arrangement of, for example, 5 x 6 elements which scans an image by means of a scanning device (not shown). (called "parallel scanning"). The detector elements 1 of the entire arrangement are controlled in the manner described in FIG. 1 by a second detector element 2 placed in front of

in the direction of the scan.

Claims (6)

  1. Photoelectric receiver for a camera, particularly for an imaging apparatus   thermal, with local adaptation of the brightness,   characterized in that it comprises at least a first detector element (1) for spot scanning the image produced by a reception optics and at least a second detector element (2) associated with one or more first detector elements and having a relatively large radiation-sensitive surface for capturing at least part of the environment of an image point   captured by a first detector element.   2. Photoelectric receiver according to the claim   1, characterized in that it comprises a line or an arrangement of first detector elements (1) for section-by-section scanning of an image ("parallel-series scanning") and a second detector element (2) for capture at least a portion of the captured image section   as a whole by the line or arrangement.   3. Photoelectric receiver according to the claim   1 or 2, characterized by the fact that the second   detector (2) has a mask or diaphragm (2.1)   opaque to the radiation allowing to modify the   face sensitive to the radiation of the detector.   4. Photoelectric receiver according to any one   Claims 1 to 3, characterized in that the   second detector element (2) comprises at least one mask or diaphragm (2.1) with a predetermined transmission so that the radiation sensitivity of the surface of the   detector can be modified locally.   5. Photoelectric receiver according to claim   3 or 4, characterized in that the mask or di-   diaphragm is an electrically controlled liquid crystal.   6. Method for local adaptation of brightness   with a device according to any of the claims   cations 1 to 5, characterized by the fact that the second   This detector determines an amplification factor with   which the signals of the first detection element or   are amplified for the formation of video signals.